Preparation Of Three-dimensional Porous Ti₃C₂T_x Materials And Research On X-band Electromagnetic Shielding Performance

MXenes is a new type of two-dimensional material with excellent electrical conductivity,high hydrophilicity and good processability.It has shown potential applications in the field of electrochemical energy storage,sensors,communications,biomedicine,actuator,etc.Especially in the field of electromagnetic interference shielding,MXenes have gradually become one of the best materials for electromagnetic pollution control based on their own high conductivity and layered structure characteristics.However,the density of the MXene（Ti₃C₂T_x）film obtained by vacuum filtration,casting or knife coating is as high as 4 g cm^-3,which greatly limits its application in aerospace and smart portable electronic devices that require lightweight electromagnetic shielding characteristics.The key to achieving light-weight and high-efficiency electromagnetic interference shielding properties is to build abundant pores between the MXene film layers and to maintain good conductive continuity in the skeleton structure.On the one hand,the pores generated between the dense MXene sheets increase more interlayer space and a large number of electromagnetic wave scattering active interfaces,which can significantly extend the transmission path of electromagnetic waves inside the material and increase the number of reflections,thereby improving the effective attenuation of electromagnetic waves.On the other hand,the dense surface and the special internal porous structure are conducive to the practical application of porous MXene materials.Based on the above,this work cleverly used acid-base neutralization to induce gelation of MXene film to construct a three-dimensional porous MXene film.The highly conductive porous frame structure increases the electromagnetic interference shielding effectiveness of the MXene film to 73 d B.In addition to its lower density(0.7 g cm^-3),the absolute shielding effectiveness of this three-dimensional porous MXene film is as high as 25445 cm²g^-1.Using the high light-to-heat conversion effect of MXene,the sunlight is focused and shined to the MXene film,which can achieve rapid foaming of the conventional dense MXene film.In this process,the sunlight induces the photothermal effect of MXene to vaporize the free water between the layers instantaneously,thereby giving a continuous cellular structure between the MXene layers.The prepared porous MXene film has light weight,high conductivity(≈1000S cm^-1)and flexibility,while also exhibiting high hydrophobicity and environmental stability.Therefore,the absolute shielding effectiveness of the 10μm-thick porous MXene film can be as high as 88333 d B cm² g^-1,which is comparable to most known porous MXene materials produced by other complex processes.In addition,a cheap laser engraving machine purchased in the market is used to shine a specific area by precisely controlling the intensity and position of the light to achieve the controllable construction of the complex structure of the porous MXene film.